1. Field of the Invention
This invention relates to a semiconductor device and a lead frame used therein, and more particularly, to a lead frame capable of effectively radiating heat generated from a semiconductor chip mounted thereon.
2. Description of the Related Art
A semiconductor chip is usually mounted on a lead frame and integrally molded with a plastic material. The lead frame is made of a metal strip and comprises a stage on which the chip is fixedly mounted and a plurality of leads to which the chip is connected.
Currently, semiconductor chips are larger in scale, have many functions, and are more integrated. As a result, the heat generated in a chip is increased. Therefore, the lead frame must be provided with more connecting pins (leads) and the plastic molded semiconductor device itself must have a construction that will effectively radiate the heat generated from the chip.
Because the lead frame has many inner leads, the gap between the leads must be minimized so that the number of leads can be maximized. in general, such gaps cannot be made smaller than a value corresponding approximately to a thickness of the lead frame. If the gap is smaller than the thickness of the lead frame, the metal strips will buckle inside a stamping press during their production. Therefore, there is a limit to the number of pins or leads that can be produced by a stamping process.
In a conventionally known semiconductor device, a stage of the lead frame and a plastic mold cooperate to radiate heat generated in a chip. However, considering the highly integrated semiconductor chips that have recently been developed, the above-mentioned solution is not sufficient for the necessary heat radiation.